Ear Canal Earbud Sound Systems, such as are used in head sets, especially of the type used in portable audio devices, such as audio players, cell phones, and in some cases in security systems head sets, and military systems, and possibly also in hearing aids, are of compact minimal size, for obvious reasons.
As a result, even though the audio quality of the actual signal may be adequate, the quality of the audio sound delivered by the speakers is often much less than is possible or desirable. This is partly due to the limitations imposed in the design by the small size of the speakers themselves.
The sound quality may be much less, where there is a noisy environment or where transmission is poor.
It is found that much of the loss of quality is due to noise induced in the speaker circuits. If this induced noise can be reduced or eliminated then the audio quality of the sound from the speakers will be both much higher, and of greater clarity.
The signals may come from sources such as tape, CD, or memory chip, or may be communication signals such as mobile phones, radio communication, or possibly hearing aids.
The audio signals may be stereo sound signals. These stereo signals are supplied as left and right hand signals. Audio signals include what can be broadly described as combining both high, medium, and low frequencies. Circuits usually provided in such ear bud speakers for this purpose are usually miniature in scale and somewhat primitive. The speakers themselves also incorporate speaker coils, and these coils are believed to contribute to the electronic noise. It is of course common place that such headsets incorporate a wire harness consisting of a pair of wires connecting to the source of audio signals, and ear buds are then connected by separate wires, one wire for each ear, each of those earbuds incorporating a speaker. In many cases the earbuds actually fit at least partially within the ear canal. In other cases they are held in some form of resilient headband, made of plastic or wire, which partially encircles the head and holds the two earbuds against the two ears.
In prior U.S. Pat. Nos. 5,615,272, and 5,519,781 and Canadian Patent 2,192,163. Inventor V. W Kukurudza, there are disclosed noise suppression circuits incorporating special “bifilar” wound coils. These bifilar coils actually comprise two coils in one. Bifilar coils consist basically of a pair of wires with the two strands wound into double coils with wire strands of one coil alternating with wire strands of the other coil. Such a bifilar coil is used in each noise suppression circuit. The bifilar coils produce a substantial reduction in electronic noise in the circuit. The bifilar coils also help to reduce the electronic noise originating in the speakers themselves.
To provide a miniaturized noise suppression circuit with such bifilar coils, of an extremely compact size, for use in the Ear Canal Earbud Sound System having the type of head sets or speaker systems described above, numerous other problems arise.
The bifilar coils develop significant internal stresses during operation. The coils must be secured so as to withstand these stresses. One approach is to provide a bifilar coil securely mounted on a single board, and the single board was located in the wire harness, but not in the ear bud itself.
This approach has met with some success. However in this system it was necessary to mount the noise suppression circuit and bifilar coils in the main wire coming from the audio device itself, before the wire is divided into two to supply each earbud. This meant that the entire headset and wire harness must be re-engineered, leading to considerable extra expense. This may lead to a certain degree of customer resistance. Earbuds each incorporate a generally speaking hollow body, containing the miniature speaker, and connections for the wire harness to the speaker.
It is now considered desirable to provide an Ear Canal Earbud Sound System with two separate miniaturized noise suppression circuits each of which actually fit within the hollow interior of a respective earbud, and each being connected between the incoming wire harness connection, and the speaker itself, and back to ground.
In order to provide this extreme degree of miniaturization, the noise suppression circuits are preferably constructed on the smallest practicable circuit board so as to fit within an existing earbud housing.
Each board must be designed and specified so as to fit within the housing of the ear bud, and the housings should preferably fit at least partially within the ear canals of the user.
Boards of this size carrying such a complex circuit, and fitting in such a limited space simply do not exist.